Valve lifters or tappets in some internal combustion engines, especially high speed automotive engines, use rollers that ride in contact with the cams of cam shafts that operate the valve lifters; i.e., that reciprocate the lifters, which are cylindrical, in cylindrical bores of the engine block. It is necessary to prevent the valve lifters from rotating in the bores in order to keep the rollers properly aligned with the cams. Lifters are typically aligned in a row along a cam shaft and are lubricated by a straight and common transverse oil passage that intersects the bores, either centrally or tangentially. Serial flow of oil through successive bores is facilitated by a peripheral groove in each lifter body. The portion of the body above and below the groove prevents loss of lubricating oil through the open ends of the bores in which the lifters reciprocate and extend.
A known approach to preventing rotation of the lifters in the bores in high speed automotive engines is to utilize a link pivotably connected at opposite ends to portions of two adjacent lifters that extend above the bores, as shown in U.S. Pat. No. 4,809,651, or to use a bar that lies on the flat surface of the engine block at the top of the bores for the valve lifters. The bar extends between and cooperates with two adjacent lifters, acting as a key to prevent rotation while allowing reciprocation, and is held in place by springs or by a suitable clamping mechanism. See, e.g., U.S. Pat. No. 3,108,580.
Valve lifters of an engine that apparently does not provide an oil passage between adjacent bores for lubrication are disclosed as being prevented from rotation by a spring clip that is located in the central plane between adjacent valve lifter bores and that is received in two adjacent bores to cooperate with flat portions of the lifters to prevent rotation. See U.S. Pat. No. 3,998,190.
The above approaches are disadvantageous, in that a link pivoted to two lifters adds moving weight, requires additional assembly steps, requires additional length to the lifters that must extend above the block, requiring headroom and requires that the lifters be made and sold in pairs. A key requires springs or clamps to retain the part in place and requires structure extending above the engine block to accommodate the key and springs or clamps and typically requires additional height of the lifter. The spring clip arrangement in U.S. Pat. No. 3,998,190 avoids many of those shortcomings, but is not applicable to an engine in which lubrication of the lifters is accomplished through an oil passage that intersects the bores to bring oil sequentially to the bores and lifters, as is the case in typical automotive engines and particularly in high speed automotive internal combustion engines.